Aircraft occupant protection system

ABSTRACT

An occupant protection system for an aircraft comprising a sensor system for sensing flight condition information and a control system, which includes an impending crash detection system and an impact detection system. The impending crash detection system receives flight information from the sensors determines whether a crash is likely to occur. If an impending crash is detected, the impending crash detection system activates impact modes of a first group of aircraft systems. The impact detection system receives flight information from the sensor system and determines whether an impact has occurred or is occurring. If an impact is detected, the impact detection system activates impact modes of a second group of aircraft systems.

TECHNICAL FIELD

The present disclosure relates generally to aircraft safety systems,including safety systems that comprise crash attenuation systems foraircraft.

DESCRIPTION OF THE PRIOR ART

Currently internal airbags are used in the automotive industry withinthe occupied volume to mitigate occupant injuries. Similarly, externalairbags have been used to attenuate decelerative loads to air and spacevehicles, such as escape modules, upon contact with the ground or water.Examples include the NASA Mars Rovers and the crew module of the GeneralDynamics/Grumman F-111.

During impact, the gas in the airbag must be vented to prevent gaspressurization and subsequent re-expansion, which may cause the occupantto accelerate backward. This effect is commonly known as rebound. Inaddition, the gas may be vented to prevent over-pressurization, whichcan cause failure of the airbag. Venting may be accomplished, forexample, through discrete vents or through a porous membrane that formsat least a portion of the skin of the airbag.

One shortcoming of prior external airbag systems is that they fail toprevent post-impact pitch-over, or “tumbling,” of an aircraft having aforward and/or lateral velocity at impact with a hard surface. Forexample, referring to FIGS. 1 a-1 e, an aircraft 10 that is equippedwith a prior external airbag system 12 is shown at different pointsduring a crash sequence from (a) to (e). The crash sequence involves theaircraft 10 having both forward and downward velocities at (a) and (b).The airbag system 12 properly deploys its airbags 14 at (b), but stillincurs serious damage due to pitch-over of the aircraft 10 as shown at(d) and (e). Thus, improvements are still needed in external airbagsystems, particularly improvements to the pitch-over stability of anaircraft equipped with an external airbag system.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, includingits features and advantages, reference is now made to the detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIGS. 1 a-1 e show a crash sequence for a helicopter equipped with aprior external airbag system;

FIG. 2 is a perspective view of a helicopter equipped with an externalairbag system;

FIG. 3 is a perspective view of an airbag used with the external airbagsystem shown in FIG. 2;

FIGS. 4 a-4 c are cross-sectional views of a vent valve in full-open,partially-open, and closed configurations, respectively;

FIG. 5 is a diagram of the vent plate shown in FIGS. 4 a-4 c;

FIG. 6 is block diagram of the helicopter shown in FIG. 2;

FIG. 7 is a block diagram illustrating the operation of the crashattenuation system of the helicopter shown in FIG. 2;

FIG. 8 shows a chart of exemplary data representative of a relationshipbetween airspeed of the helicopter and open vent area;

FIGS. 9 a-9 d show a crash sequence for a helicopter equipped with anexternal airbag system according to the present disclosure;

FIG. 10 shows a cross-sectional view of an airbag of the external airbagsystem of the present disclosure;

FIG. 11 shows a perspective view of a helicopter equipped with analternative external airbag system;

FIG. 12 shows a block diagram of an occupant protection system;

FIG. 13 shows a block diagram of a more detailed embodiment of theoccupant protection system shown in FIG. 12;

FIG. 14 shows a partial top view of a venting system for a crashattenuation system;

FIG. 15 shows a partially sectioned side view of a first embodiment ofthe venting system shown in FIG. 14;

FIG. 16 shows a partially sectioned side view of a second embodiment ofthe venting system shown in FIG. 14;

FIG. 17 shows a cross-sectional side view of the vent passage of theventing system shown in FIG. 14, illustrating a first embodiment of avent valve for the venting system; and

FIG. 18 shows a cross-sectional side view of the vent passage of theventing system shown in FIG. 14, illustrating a second embodiment of avent valve for the venting system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present disclosure provides for a number of safety improvements foraircraft, including an impact detection system, an impending crashdetection system, and an inflatable crash attenuation system for anaircraft.

The inflatable crash attenuation system can comprise an airbag that isinflated prior to impact and controllably vented during impact so as toprevent aircraft pitch-over. The system can be used on a number ofdifferent types of aircraft, for example, helicopter, fixed wingaircraft, and other aircraft, and in particular those that arerotorcraft. The system improves on the prior art by providing automaticcontrol of the venting valves based on sensed crash conditions, therebyeffectively shifting the center of impact pressure and preventingaircraft pitch-over.

FIG. 2 shows a helicopter 100 incorporating the crash attenuation systemaccording to the present disclosure. Helicopter 100 comprises a fuselage102 and a tail boom 104. A rotor 106 provides lift and propulsive forcesfor flight of helicopter 100. A pilot sits in a cockpit 108 in a forwardportion of fuselage 102, and a landing skid 110 extends from a lowerportion of fuselage 102 for supporting helicopter 100 on a rigidsurface, such as the ground.

A problem with rotor 106 or the drive system for rotor 106 maynecessitate a descent from altitude at a higher rate of speed than isdesirable. If the rate is an excessively high value at impact with theground or water, the occupants of helicopter 100 may be injured andhelicopter 100 may be severely damaged by the decelerative forcesexerted on helicopter 100. To reduce these forces, an airbag assembly111 comprising inflatable, non-porous airbags 112, 114 is installedunder fuselage 102. Though not shown in the drawings, airbags 112, 114are stored in an uninflated condition and are inflated under the controlof a crash attenuation control system (described below).

FIG. 3 is an enlarged view of airbag 112, which has a non-porous bladder116, which is sealed to a housing 117 having a plurality of discretevents 118. Airbag 112 is shown in FIG. 3, but it should be noted thatairbags 112 and 114 can have generally identical configurations. In apreferred embodiment, the bladder 116 is formed of a fabric thatcomprises resilient material such as Kevlar and/or Vectran. Vents 118communicate with the interior of bladder 116, allowing for gas tocontrollably escape from within the airbag 112. In the embodiment shown,vents 118 are open to the ambient air, though vents 118 may be connectedto a closed volume, such as another airbag or an accumulator (notshown). Also, while a plurality of vents are shown in the embodimentillustrated in FIG. 3, alternative embodiments can include only a singlevent 118.

Referring to FIGS. 4 a-4 c, each vent 118 has a vent valve 120 forcontrolling the flow of gas through vent 118. Vent 118 and vent valve120 together form a vent passage 122 for channeling gas flowing out ofairbag 112. Each vent valve 120 is sealingly mounted in housing 117 (orbladder 116 in some embodiments) to prevent the leakage of gas aroundvent 118, which forces venting gas to flow through passage 122. A ventplate 124 is configured to be moveable between an open position, forexample shown in FIG. 4 a, at least one intermediate position, forexample as shown in FIG. 4 b, and a closed position, for example asshown in FIG. 4 c. FIG. 4 a shows vent plate 124 in the open position,or open state, in which a maximum amount of gas is allowed to flowthrough passage 122 from within airbag 112. FIG. 4 b shows vent plate124 in an intermediate position, or intermediate state, in which aselected amount of gas less than the maximum is allowed to flow throughpassage 122 from within airbag 112. FIG. 4 c shows vent plate 123 in theclosed position, or closed state, in which gas is prevented from flowingout of airbag 112 through the passage 122. Though only a singleintermediate position is shown, it should be understood that variousadditional intermediate positions can be selected in order to controlthe amount of gas that is allowed to escape from within the airbag 112through the vent 118. Also, while the vent valve 120 is shown as asliding valve, it will be understood by one skilled in the art that ventvalve 120 may alternatively be other suitable types of valves. Controlof vent valves 120 may be accomplished though any number of means,including, for example, electrorheological means. In some embodiments,the vents 118 can be sealed with an optional pop-off pressure releasemechanism, preferably a pressure sensitive fabric 125. In suchembodiments, once the fabric 125 pops off, the vent valve 120 controlsrelease of the pressurized air inside the airbag 112, 114.

Referring next to FIG. 5, as will be discussed in greater detail below,each vent plate 124 can be selectively positioned to any positionbetween a full open position and a full closed position. In the viewshown in FIG. 5, the hatched area 127 represents the open vent area,through which gas can escape from within an airbag 112 or 114 throughpassage 122. The vent plate can be moved a distance A according to adesired amount of open vent area 127. The open vent area 127 will be atotal open vent area “S” if there is only one vent 118; otherwise, theopen vent area 127 of each vent 118 is summed to be a total vent area“S.” The total vent area S is a function of crash conditions:S=f({dot over (x)},ż,θ,φ,{dot over (θ)},{dot over (φ)},Δ, . . . )where {dot over (x)} represents forward velocity, ż represents downwardor sink velocity, θ represents pitch angle, φ represents roll angle,{dot over (θ)} represents pitch rate, {dot over (φ)} represents rollrate, and Δ represents the slope of the impact surface (e.g., the slopeof the ground).

FIG. 6 shows airbags 112 and 114 mounted to a lower portion of fuselage102 and show additional components of the crash attenuation systemaccording to the present disclosure. A computer-based control system126, which is shown mounted within fuselage 102, is provided forcontrolling the operation of components associated with airbags 112,114. Each airbag 112, 114 has a gas source 128, such as a gas generator,for inflation of the airbags 112, 114. In some embodiments, a secondarygas source, such as compressed gas tank (not shown), can be provided forpost-crash re-inflation of airbags 112, 114 so that the airbags 112, 114can be used as floatation devices in the event of a water landing. Thegas source 128 may be of various types, such as gas-generating chemicaldevices or compressed air, for providing gas for inflating airbags 112,114. In addition, the crash attenuation system has a sensor system 130for detecting crash conditions used to determine the total vent area S,such as rate of descent and/or ground proximity. Airbags 112, 114 canalso have a water-detection system (not shown), which may have sensorsmounted on fuselage 102 for detecting a crash in water. Gas source 128,vent valves 120, and sensor system 130 are in communication with controlsystem 126, allowing control system 126 to communicate with, monitor,and control the operation of these attached components. In addition,control system 126 may be in communication with a flight computer orother system for allowing the pilot to control operation of the crashattenuation system. For example, the pilot may be provided means tooverride, disarm, or arm the crash attenuation system.

The sensor system 130 is shown in FIG. 6 as a discrete component for thesake of convenience. However, it should be noted that actualimplementations of the sensor system 130 can comprise a number ofcomponents that are located at various locations on the helicopter 100.The sensor system 130 can include, for example, sensors for detectingpitch and roll attitude, pitch and roll rate, airspeed, altitude, rateof descent, and slope of the impact surface.

Referring next to FIG. 7, an exemplary embodiment of the sensor system130 is configured to detect various crash conditions, which can include,for example, one or more of the sink speed, forward speed, pitch androll attitude, pitch and roll rate, and proximity to the ground of thehelicopter 100. The control system 126 receives data from the sensorsystem 130 representative of the detected crash conditions. In apreferred embodiment, the control system 126 is a microprocessor-basedsystem configured to operate as a crash predictor. When excessiveoncoming velocity of the ground within a certain altitude range isdetected by the control system 126, the gas source 128 is triggered toinflate the airbags 112, 114 (indicated at box 126A) prior to impact ofthe helicopter 100 with the ground. At the same time, the control system126 activates the vent valves 120 to adjust the open vent area based onan active vent valve algorithm as indicated at box 1268.

FIG. 8 shows an example of a relationship that can be used by thecontrol system 126 for adjusting the open vent areas at 126B. In FIG. 8,a chart is shown that illustrates a relationship between open vent areaand forward velocity of a helicopter for a given sink velocity of 36feet per second. The line 134 maps open vent areas to forward velocitiesfor the forward airbag 112, while the line 136 maps open vent areas toforward velocities for the aft airbag 114. It should be appreciated thatthe relationship will vary for different sink velocities. Therelationship will also vary depending on a number of other factors, forexample aircraft characteristics, such as aircraft weight and balance,and the number and characteristics of the airbags. The data can bedetermined using known flight simulation techniques, for examplesimulation software, for simulating crash results. Using suchtechniques, data can be collected based on simulation of crash resultsfor various crash conditions and open vent areas.

FIGS. 9 a through 9 d illustrate operation of the crash attenuationsystem. In operation, if an impending crash is sensed by sensor system130, for example, by excessive oncoming rate of the ground within acertain attitude range, control system 126 triggers gas source 128 toinflate airbags 112, 114 at the appropriate time to allow inflation justas airbags 112, 114 contact the impact surface (ground or water).

FIG. 9 a shows an impending crash onto ground 132, which is sensed bythe control system 126 based on data received from the sensor system130. At FIG. 9 b, gas source 128 is triggered, causing airbags 112 and114 to inflate just prior to contact with ground 132. The control system126 also calculates the open vent areas for each of the airbags 112,114. In this case, the control system 126 determines that the crashconditions correspond to the line 138 shown in FIG. 8, which requiresthe open vent area of aft airbag 114 be greater than the open vent areaof forward airbag 112. Accordingly, at FIG. 9 c the open vent area ofaft airbag 114 is set to an area of about 0.0205 square meters and theopen vent area of forward airbag 112 is set to an area of about 0.0145square meters. Thus, as shown in FIG. 9 c, the aft airbag 114 deflatesfaster than the forward airbag 112. As a result, as shown at FIG. 9 d,the helicopter 100 comes to a stop without experiencing a pitch-over.

Referring next to FIG. 10, a cross-section of a preferred embodiment ofan airbag 112, 114 is shown. The hatched area 140 represents the portionof the airbag 112, 114 that is adjacent to the underside of the fuselage102. The arrow 142 points towards the forward end of the helicopter 100.The broken line 144 is the widest portion of the airbag 112, 114 betweenthe top (hatched area 140) and bottom 146 of the airbag 112, 114. Asshown in FIG. 10, for a width W of the airbag at line 144, the distanceD1, which is the distance between the top 140 and the line 144, and thedistance D2, which is the distance between the bottom 146 and the line144, are equal and determined based on the following relationship:

${D\; 1},{{D\; 2} = \frac{W}{2\sqrt{3}}}$This geometry maximizes crush distance for optimal energy absorptionmanagement. Also, the curved region 148 provides anti-plow,anti-scooping geometry to assist in preventing pitch-over of thehelicopter 100.

Referring next to FIG. 11, an alternative embodiment of the helicopter200 is shown. As mentioned above, while the present crash attenuationsystem has been discussed primarily in connection with two airbags 112,114, alternative embodiments can have additional airbags. For example,the helicopter 200 shown in FIG. 11 has an airbag assembly 211comprising four airbags 212, 213, 214, and 215. Like the helicopter 100,the helicopter 200 comprises a fuselage 202 and a tail boom 204. A rotor206 provides lift and propulsive forces for flight of helicopter 200. Apilot sits in a cockpit 208 in a forward portion of fuselage 202, and alanding skid 210 extends from a lower portion of fuselage 202 forsupporting helicopter 200 on a rigid surface, such as the ground.

A problem with rotor 206 or the drive system for rotor 206 maynecessitate a descent from altitude at a higher rate of speed than isdesirable. If the rate is an excessively high value at impact with theground or water, the occupants of helicopter 200 may be injured andhelicopter 200 may be severely damaged by the decelerative forcesexerted on helicopter 200. To reduce these forces, inflatable,non-porous airbags 212, 213, 214, and 215 are installed under fuselage202. Though not shown in the drawings, airbags 212, 213, 214, and 215are stored in an uninflated condition and are inflated under the controlof a crash attenuation control system.

The crash attenuation system of the helicopter 200 can operate asdiscussed above in connection with the helicopter 100. In addition,compared to the helicopter 100, the helicopter 200 provides additionallateral roll-over prevention capabilities. Each of the airbags 212, 213,214, and 215 is independently actively vented during a crash sequence.Thus, if the helicopter 200 is approaching the ground with a lateralvelocity, the airbags 212 and 214, which are located along one side ofthe helicopter 200, can be vented more or less than the airbags 213 and215, which are located along the other side of the helicopter 200, asnecessary based on detected crash conditions in order to prevent thehelicopter 200 from rolling over after impact with the ground.

The above disclosure describes a system and method for activelycontrolling the venting of external airbags based on sensed crashconditions, such as airspeed, sink speed, pitch attitude, roll attitude,pitch rate, and roll rate. This active venting of the external airbagscauses different airbags located at different locations of an aircraftexterior to deflate at different rates upon impact, thereby shifting anaircraft's center of impact pressure.

Turning next to FIG. 12, a block diagram shows an occupant protectionsystem (OPS) 300. The OPS 300 provides a control system that computesvarious impact scenarios (forward/vertical velocities, pitch/rollattitudes, pitch/roll velocities, impact angle, and likely surfacecharacteristics) based upon signals detected by various sensors 302,electronic maps, and other available data. The control system algorithmis then used to actively control and schedule various safety systemsthroughout the aircraft. The OPS 300 includes a sensor system 302, whichcan serve as an embodiment of the sensor system 130 described above. TheOPS 300 also includes an impact detection system 304 and an impendingcrash detection system 306, either one or both of which can serve as thecontrol system 126 described above. The impending crash detection system306 is configured for detecting an imminent crash, while the impactdetection system 304 is configured for detecting the actual occurrenceof a crash.

The impending crash detection system 306 is in communication with one ormore sensors of the sensor system 302. While the aircraft is in flight,the impending crash detection system 306 can be configured forperiodically receiving information from one or more sensors of sensorsystem 302 as well as other available data from other aircraft systems.The crash detection system 306 is configured to evaluate the receivedinformation and determine whether there is excessive oncoming velocityof the ground within a certain altitude range, as would occur in theevent of an imminent impact. If an impending crash is detected, thecrash detection system 306 is configured to communicate with one or moreimpending crash safety systems 310 in order to initiate a series ofactions to protect the occupants of the aircraft.

The impact detection system 304 is configured for detecting whether anactual impact is occurring or has occurred. While the aircraft is inflight, the impact detection system 304 can be configured forperiodically receiving information from one or more sensors of sensorsystem 302 as well as other available data from other aircraft systems.The impact detection system 304 is configured to evaluate the receivedinformation and determine whether an impact is occurring or hasoccurred, for example by detecting a sudden stop or drop in forwardand/or downward velocity as would occur during an impact. If an impactis detected, the impact detection system 304 is configured tocommunicate with one or more impact safety systems 308 in order toinitiate a series of actions to protect the occupants of the aircraft.

Turning next to FIG. 13, a more detailed block diagram shows an exampleof an embodiment of the OPS 300. In the illustrated embodiment, thesensor system 302 includes one or more of the following: one or moreaccelerometers 312, a Global Positioning System (GPS) and/or InertialNavigation System (INS) 314, a Helicopter Terrain Awareness WarningSystem (HTAWS) and/or Enhanced Ground Proximity Warning System (EGPWS)316, an altimeter 318, and a Transponder Collision Avoidance System(TCAS) 320.

Impact detection system 304 includes impact detection logic 304 a, whichreceives and evaluates data from one or more accelerometers 312. Datafrom the accelerometers 312 can be evaluated by the impact detectionsystem 304 in order to determine whether an impact is occurring or hasoccurred. If an actual impact is detected, the impact detection system304 can control one or more of the impact safety systems 308 to take oneor more predetermined actions that would be desirable in the event of acrash. FIG. 13 shows the following examples of impact safety systems308: internal airbags 322, collapsible cyclic stick 324, soft pedals326, fuel shutoff valves 328, fuel ventilation 330, fire extinguishers332, egress lighting 334, door latches 336, and an Emergency LocatorTransmitter (ELT) 338.

The impact safety systems 308 can include conventional systems orsystems that improve on conventional systems. For example, the internalairbags 322 can be of the type known in the art for use in aircraft andautomobiles in order to help prevent injuries during a crash.

A collapsible cyclic stick is disclosed in U.S. Pat. No. 5,431,361 toCarnell et al., which is hereby incorporated by reference. Thecollapsible cyclic stick disclosed by Carnell et al. is designed for usein combination with an energy attenuating stroking crew seat. TheCarnell et al. cyclic stick is mechanically connected to the seat suchthat the cyclic stick is displaced as a result of the stroking action ofthe seat during a severe crash. The collapsible cyclic stick 324 can besimilar to the Carnell cyclic stick, except that an actuator or the likeis used to displace or collapse the collapsible cyclic stick 324according to control signals from the impact detection system 304.Similarly, the soft pedals 326 are controllable by the impact detectionsystem 304 to collapse, displace, or become freely movable if an impactis detected. These measures help prevent injury to the pilot during acrash that could otherwise occur due to forceful contact with the cyclicstick and/or pedals.

A number of systems are controlled in order to reduce the risk of fireduring and after an impact. For example, the fuel shutoff valves 328 canbe controlled to close and/or the fuel pump can be shut off, for examplevia a Full Authority Digital Engine Control (FADEC) if the aircraft isso equipped. Similarly, fuel ventilation 330 can be closed in order toprevent the release of flammable vapors into a crash environment thatmight include ignition sources, such as sparking from damaged wiring.Also, fire extinguishers 332 can be armed and/or activated.

Other systems can be controlled for making it easier for the pilots andcrew to exit the aircraft, such as activation of egress lighting 334,unlocking and/or opening door latches 336. An active rotor brake canstop the rotating blades overhead to protect the occupant's heads. Anautomatic seatbelt release would speed egress in the event of a waterlanding and the aircraft filling with water. Finally, an EmergencyLocator Transmitter (ELT) 338 can be activated for allowing the aircraftto be located by search parties.

In addition, the impact detection system 304 can issue an impactdetection signal to a float control 340. The float control 340 alsoreceives data from an immersion sensor 342 and from a terrain database344. Based on the received data, the float control 340 can be configuredto activate external airbags and/or life rafts 346 in the event of awater landing or crash. Floats would be configured to preserve thebreathable airspace within the aircraft in case the aircraft rolls orflips over.

These and other systems can be activated by the impact detection system304 since they are desirable in the event of an actual crash, but shouldnot be activated unless an actual crash has occurred because they wouldhinder the operation of the aircraft. Other systems designated asimpending crash safety systems 310 can be controlled for improvingsafety during impact, but do not hinder operation of the aircraft sothey can be activated earlier than the impact safety systems 308 beforean actual crash has occurred.

Impending crash detection system 306 includes impending crash detectionlogic 306 a, which receives and evaluates data from sensor systems 302,which can include one or more accelerometers 312, GPS and/or INS 314,HTAWS and/or EPGWS 316, radar altimeter 318, and TCAS 320. The impendingcrash detection system 306 also receives airspeed data from air datacomputer (ADC) 360 via a sea state, wind vector estimator 362. Data fromthe sensor system 302 can be evaluated by the impending crash detectionsystem 306 in order to determine whether an impact is likely to occur.If an impending crash is detected, the impending crash detection system306 can control one or more of the impending crash safety systems 310 totake one or more predetermined actions that would be desirable in theevent of an impending crash. FIG. 13 shows the following examples ofimpending crash safety systems 310: automatic flare system 348, activerestraint system 350, active seat control system 352, as well as a crashattenuation system, which can be a crash attenuation system according toany of the embodiments disclosed herein, having an active ventcontroller 354 and external airbags 356.

The impact safety systems 308 can include conventional systems orsystems that improve on conventional systems. For example, the automaticflare system 348 can be of the type of maneuver known for deceleratingthe helicopter in order to reduce forward speed and decrease the rate ofdescent. The impending crash detection system 306 can also send data toa crash heading command controller 364, which can determine a vehiclestate (velocities, rates, accelerations, etc) and make adjustments tothe flight control system 366. The active restraint system 350 caninclude an haul-back restraint system where shoulder restraints areretracted in order to straighten the spine of the pilot or crewmember.This helps to properly position the person for impact in order to reducethe chances of a back or neck injury to the extent possible. The activeseat control system 352 can be activated to control seats to strokedownwardly during a crash in order to absorb some of the force ofimpact. The impending crash detection system 306 can also activate anactive landing gear controller 370 to extend and stiffen landing gear372 for maximum energy absorption.

Turning now to FIGS. 14-21, various embodiments of venting systems forthe crash attenuation systems disclosed herein will be described. Whilethe venting system is described below in connection with a singleairbag, it should be appreciated that multiple venting systems can beused with multiple airbags on a single aircraft. For example, theventing systems shown in FIGS. 14-21 can be used with a two-airbag crashattenuation system such as the one shown in FIG. 2, and can also be usedwith a four-airbag crash attenuation system such as the one shown inFIG. 11.

FIG. 14 shows a partial top view of a venting system 400 for a crashattenuation system comprising an airbag 402 (partially shown in FIG. 14)and a housing 404. The venting system 400 would ordinarily be disposedon the underside of an aircraft; however, no aircraft is shown in FIG.14 in order to allow for an unobstructed view of the venting system 400.The airbag 402 can be identical to airbags 112 and 114, and the housing404 can be identical to the housing 117. The venting system 400 isconfigured for controlling whether gas is allowed to escape from withinthe airbag 402 and housing 404. The venting system 400 can be controlledby a control system such as control system 126 or controller 354 asdescribed above. FIG. 14 also shows an inflator 406 that is controllableby a control system, such as control system 126 or controller 354, forinflating the airbag 402.

The venting system 400 includes a vent passage 408. The vent passage 408is formed by rigid substrates, for example formed of sheet metal oranother rigid material. The vent passage 408 extends between a firstopening 410 within the housing 404, and a second opening 412 external tothe airbag 402 and housing 404. One or more vent valves 414 are disposedwithin the vent passage 408. The vent valves 414 can include activevalves that are controllable for regulating the flow of air through thevent passage 408 as described above in connection with vent 118. Thevent valves 414 can also include pop-off valves that are designed toburst under the force of a predetermined amount of air pressure.

Turning next to FIG. 15, a partially-sectioned side view is shown ofventing system 400, as well as airbag 402 and housing 404 all supportedby an aircraft fuselage 416. In this embodiment, the upper side of thevent passage 408 is flush with the under side of the fuselage 416. InFIG. 15, the airbag 402 is inflated and supporting at least a portion ofthe fuselage 416. In this situation, the airbag 402 is compressed by theweight of the aircraft and the upper portion of the airbag 402 ispressed against the under side of the fuselage 416 and the vent passage408. The vent passage 408 is at least long enough to extend beyond theupper portion of the airbag 402. Otherwise, the upper portion of theairbag 402 would form a seal that could prevent air from escaping fromwithin the airbag 402.

In FIG. 15, the vent passage includes a vent valve 414 that can becontrolled to move to any position between the fully open position shownin solid lines and the fully closed position shown in broken lines. Asdiscussed above in connection with vent 118 and vent valve 120, variousintermediate positions of the vent valve 414 between the fully openedand fully closed positions can be selected in order to control theamount of gas that is allowed to escape from within the airbag 402through the vent passage 408. While the vent valve 414 is fully orpartially opened, air can escape from within the airbag 402 through thevent passage as indicated by arrows 418-420. While the vent valve 414 isfully closed, the vent passage 408 is sealed by the vent valve 414 sothat air cannot escape through the vent passage 408. Also, in the eventof a water landing, the vent valve 414 can be fully closed in order toboth retain air within the airbag 402 and prevent the airbag 402 fromfilling with water. As shown in FIG. 14, alternative embodiments caninclude multiple vent valves 414 in series.

Turning next to FIG. 16, an alternative embodiment is shown wherein thevent passage 408 is at least partially contained within the fuselage 416of the aircraft. While the bottom side of the vent passage 408 is shownflush with the under side of the fuselage 416, in alternativeembodiments the vent passage 408 can extend through other portions ofthe aircraft. In the illustrated embodiment, the second opening 412opens to the under side of the fuselage 416. In alternative embodiments,the second opening can open to the top, side, or other part of theaircraft so long as the second opening will not be obstructed by theairbag 402.

The embodiment shown in FIG. 16 also shows an example of an embodimentof the venting system 400 having multiple vent valves 414. The ventingsystem 400 as shown in FIG. 16 includes a pop-off vent valve 414 a inseries with an active vent valve 414 b. Still further embodiments caninclude any number of vent valves 414 as desired.

Turning next to FIGS. 17 and 18, more detailed views are shown ofexamples of embodiments of active vent valves 414 c and 414 d,respectively, that can be used with the venting system 400 incombination with, or in place of, the active vent valve 120 describedabove in connection with vent 118. It should be appreciated that theseare only examples, and that many modifications are possible to theseembodiments, and that there are many other types of controllable valvescan be used as an active vent valve 414.

Referring to FIG. 17, vent valve 414 c is an embodiment of an activevent valve 414 that can be controlled to be fully opened (shown inphantom), fully closed (shown in solid lines), or partially opened toany of a continuous range of partially-opened positions between thefully open and fully closed positions for regulating the flow of airthrough the vent passage 408. In the view shown in FIG. 17, air travelsfrom the airbag 402 in the direction indicated by arrow 426. The ventvalve 414 c includes a vent plate 430 that is hingedly connected to atleast a portion of the vent passage 408. The vent plate 430 isconfigured to fully seal the vent passage 408 when in the closedposition (shown in solid lines) such that air cannot flow through thevent passage 408 when the vent plate 430 is in the fully closedposition. An actuator 432 is attached to the vent plate 430. Theactuator 432 is configured for moving the vent plate 430 to any desiredposition, between and including the closed position (shown in solidlines) and fully open position (shown in broken lines) as directed by acontrol system such as control system 126 or controller 354 as describedabove.

In the embodiment shown in FIG. 17, the vent passage 408 includes ashoulder 434. The shoulder 434 helps provide for a better seal betweenthe vent passage 408 and the vent plate 430. The shoulder 434 can alsoact as a stop, preventing the vent plate 430 from hyperextending beyondthe fully closed position towards the airbag 402, for example under theforce of incoming water as might otherwise occur if the airbag 402 wereto deploy during a water landing or crash. In alternative embodiments,the shoulder 434 can extend up into the vent passage 408 rather thanextending outwardly from the vent passage 408 as shown in FIG. 17.

Referring next to FIG. 18, the vent valve 414 d includes many of thesame elements as vent valve 414 c, and therefore retains many of thesame element numbers. The main difference between vent valve 414 c andvent valve 414 d is that vent valve 414 d includes a controllablelocking system 440. The locking system 440 includes an actuator 442 orthe like that can be controlled to move between a retracted positionshown in solid lines and an extended position shown in broken lines.When the actuator 442 is in the retracted position, the vent plate 430can be moved by actuator 432 from the closed position to any desiredpartially or fully opened position. When the actuator 442 is in theextended position, the vent plate 430 is locked into the fully closedposition.

While this disclosure has referenced at least one illustrativeembodiment, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments, will be apparentto persons skilled in the art upon reference to the description.

The invention claimed is:
 1. An occupant protection system for anaircraft, the system comprising: a sensor system for sensing flightinformation associated with the flight of the aircraft; a control systemincluding an impending crash detection system and an impact detectionsystem; a first group of aircraft systems each configurable for impactmode, wherein: the impending crash detection system receives at leastsome of the flight information from the sensor system and determineswhether a crash is likely to occur based at least in part on thereceived flight information, the impending crash detection system isconfigured to provide an impending crash signal to the first group ofaircraft systems if the impending crash detection system determines thata crash is likely to occur, and the first group of aircraft systems areconfigured to automatically initiate impact mode upon receipt of theimpending crash signal from the impending crash detection system; and asecond group of aircraft systems each configurable for impact mode,wherein: the impact detection system receives at least some of theflight information from the sensor system and determines whether animpact has occurred based at least in part on the received flightinformation, wherein the impact detection system is configured toprovide an impact signal to the second group of aircraft systems if theimpact detection system determines that an impact has occurred, whereinthe second group of aircraft systems are configured to automaticallyinitiate impact mode upon receipt of the impact signal from the impactdetection system, wherein the second group of aircraft systems comprisesat least one of a soft pedal system, a fuel shutoff system, a fuel tankventilation system, a fire extinguisher system, an egress lightingsystem, a door latch system, an emergency locator transmitter system. 2.The occupant protection system of claim 1, wherein the second group ofaircraft systems further comprises at least one of a collapsible cyclicstick system and an internal airbag system.
 3. The occupant protectionsystem of claim 1, wherein the first group of aircraft systems comprisesat least one of an automatic flare maneuver system, an active restraintsystem, an active seat system, an external airbag system.
 4. Theoccupant protection system of claim 1, wherein the sensor systemcomprises at least one of a global positioning system (GPS), an inertialnavigation system (INS), a Helicopter Terrain Awareness Warning System(HTAWS), an enhanced ground proximity warning system (EGPWS), a radaraltimeter, a transponder collision avoidance system (TCAS), an immersionsensor system, one or more accelerometers.
 5. The occupant protectionsystem of claim 1, wherein the control system includes an electroniccontrol system comprising a processor and a memory.
 6. The occupantprotection system of claim 1, wherein the impact detection systemreceives at least some of the flight information from an accelerometerand determines whether an impact has occurred based at least in part onthe received flight information from the accelerometer.
 7. The occupantprotection system of claim 6, wherein the impact detection systemdetermines whether an impact has occurred based at least in part on atleast a predetermined amount of deceleration being detected by theaccelerometer.
 8. The occupant protection system of claim 1, wherein theimpending crash detection system determines whether a crash is likely tooccur based at least in part on received flight information aboutdistance to ground and speed of the aircraft in the direction of theground.
 9. The occupant protection system of claim 1, wherein the firstgroup of aircraft systems are each configurable for impact mode forpreparing the aircraft for impact such that the crash environment of theaircraft is improved for aircraft occupants while allowing for continuedpiloting of the aircraft.
 10. The occupant protection system of claim 1,wherein the second group of aircraft systems are each configurable forimpact mode for preparing the aircraft for impact such that the crashenvironment of the aircraft is improved for aircraft occupants in such away that may hinder further piloting of the aircraft.
 11. A method foroccupant protection for an aircraft, the method comprising: using asensor system, sensing flight information associated with the flight ofthe aircraft; receiving, at an impending crash detection system, atleast some of the flight information from the sensor system;determining, using the impending crash detection system, whether a crashis likely to occur based at least in part of the received flightinformation; providing an impending crash signal from the impendingcrash detection system to a first group of aircraft systems if theimpending crash detection system determines that a crash is likely tooccur, wherein the first group of aircraft systems are configured toautomatically initiate an impact mode upon receipt of the impendingcrash signal from the impending crash detection system; receiving, at animpact detection system, at least some of the flight information fromthe sensor system; determining, using the impact detection system,whether an impact has occurred based at least in part on the receivedflight information; providing an impact signal from the impact detectionsystem to a second group of aircraft systems if the impact detectionsystem determines that an impact has occurred, wherein the second groupof aircraft systems are configured to automatically initiate an impactmode upon receipt of the impact signal from the impact detection system,and wherein the second group of aircraft systems comprises at least oneof a soft pedal system, a fuel shutoff system, a fuel tank ventilationsystem, a fire extinguisher system, an egress lighting system, a doorlatch system, an emergency locator transmitter system.
 12. The method ofclaim 11, wherein the second group of aircraft systems further comprisesat least one of a collapsible cyclic stick system and an internal airbagsystem.
 13. The method of claim 11, wherein the first group of aircraftsystems comprises at least one of an automatic flare maneuver system, anactive restraint system, an active seat system, an external airbagsystem.
 14. The method of claim 11, wherein the sensor system comprisesat least one of a global positioning system (GPS), an inertialnavigation system (INS), a Helicopter Terrain Awareness Warning System(HTAWS), an enhanced ground proximity warning system (EGPWS), a radaraltimeter, a transponder collision avoidance system (TCAS), an immersionsensor system.
 15. The method of claim 11, wherein the control systemincludes an electronic control system comprising a processor and amemory.
 16. The method of claim 11, wherein the receiving, at the impactcrash detection system, of at least some of the flight informationincludes receiving at least some of the flight information from anaccelerometer; and wherein the determining, using the impact detectionsystem, of whether an impact has occurred is based at least in part onthe received flight information from the accelerometer.
 17. The methodof claim 16, wherein the determining, using the impact detection system,of whether an impact has occurred is based at least in part on at leasta predetermined amount of deceleration being detected by theaccelerometer.
 18. The method of claim 11, wherein the determining,using the impending crash detection system, of whether a crash is likelyto occur is based at least in part on received flight information aboutdistance to ground and speed of the aircraft in the direction of theground.
 19. The method of claim 11, wherein the first group of aircraftsystems are each configurable for impact mode for preparing the aircraftfor impact such that the crash environment of the aircraft is improvedfor aircraft occupants while allowing for continued piloting of theaircraft.
 20. The method of claim 11, wherein the second group ofaircraft systems are each configurable for impact mode for preparing theaircraft for impact such that the crash environment of the aircraft isimproved for aircraft occupants in such a way that may hinder furtherpiloting of the aircraft.